const express = require('express');
const router = express.Router();
const { getDb } = require('../db');

router.get('/', (req, res) => {
  try {
    const db = getDb();
    const rows = db.prepare('SELECT * FROM products ORDER BY name').all();
    res.json(rows);
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

router.get('/:id', (req, res) => {
  try {
    const db = getDb();
    const row = db.prepare('SELECT * FROM products WHERE id = ?').get(req.params.id);
    if (!row) return res.status(404).json({ error: 'Product not found' });
    res.json(row);
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

router.post('/', (req, res) => {
  try {
    const db = getDb();
    const { name, price = 0, quantity_on_hand = 0, low_stock_threshold = 0 } = req.body;
    if (!name || name.trim() === '') {
      return res.status(400).json({ error: 'Name is required' });
    }
    const result = db.prepare(
      'INSERT INTO products (name, price, quantity_on_hand, low_stock_threshold) VALUES (?, ?, ?, ?)'
    ).run(name.trim(), Number(price), Number(quantity_on_hand), Number(low_stock_threshold));
    const row = db.prepare('SELECT * FROM products WHERE id = ?').get(result.lastInsertRowid);
    res.status(201).json(row);
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

router.put('/:id', (req, res) => {
  try {
    const db = getDb();
    const { name, price, quantity_on_hand, low_stock_threshold } = req.body;
    const existing = db.prepare('SELECT * FROM products WHERE id = ?').get(req.params.id);
    if (!existing) return res.status(404).json({ error: 'Product not found' });
    const n = name !== undefined ? name.trim() : existing.name;
    const p = price !== undefined ? Number(price) : existing.price;
    const q = quantity_on_hand !== undefined ? Number(quantity_on_hand) : existing.quantity_on_hand;
    const t = low_stock_threshold !== undefined ? Number(low_stock_threshold) : existing.low_stock_threshold;
    if (!n) return res.status(400).json({ error: 'Name is required' });
    db.prepare(
      'UPDATE products SET name = ?, price = ?, quantity_on_hand = ?, low_stock_threshold = ? WHERE id = ?'
    ).run(n, p, q, t, req.params.id);
    const row = db.prepare('SELECT * FROM products WHERE id = ?').get(req.params.id);
    res.json(row);
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

router.patch('/:id/stock', (req, res) => {
  try {
    const db = getDb();
    const { adjustment } = req.body;
    if (adjustment === undefined || adjustment === null) {
      return res.status(400).json({ error: 'adjustment is required' });
    }
    const delta = Number(adjustment);
    const row = db.prepare('SELECT * FROM products WHERE id = ?').get(req.params.id);
    if (!row) return res.status(404).json({ error: 'Product not found' });
    const newQty = row.quantity_on_hand + delta;
    if (newQty < 0) {
      return res.status(400).json({ error: 'Quantity would go negative' });
    }
    db.prepare('UPDATE products SET quantity_on_hand = ? WHERE id = ?').run(newQty, req.params.id);
    const updated = db.prepare('SELECT * FROM products WHERE id = ?').get(req.params.id);
    res.json(updated);
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

router.delete('/:id', (req, res) => {
  try {
    const db = getDb();
    const result = db.prepare('DELETE FROM products WHERE id = ?').run(req.params.id);
    if (result.changes === 0) return res.status(404).json({ error: 'Product not found' });
    res.status(204).send();
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

module.exports = router;